Many functions of radio communication equipment have been implemented via hardware since utilization of radio communications.
Radio communication methods including frequencies and modulation methods are diversified, and a number of radio communication methods coexist today.
Because hardware is required for each frequency and each modulation method in order to support a plurality of radio communication methods, there is a trend toward upsizing of radio equipment.
Therefore, software defined radio equipment which can support a plurality of radio communication methods by changing its frequency and its modulation method using software has been desired.
Because software defined radio equipment does not have to provide hardware for each frequency and every modulation method, the radio equipment can be downsized.
A power amplifier mounted in software defined radio equipment needs to cover all a frequency range defined by software, and is required to operate over a large frequency range.
As a method of acquiring a high-efficient characteristic, a high-output characteristic and a wide-band characteristic in a case of implementing such a power amplifier using a single amplifier, a method of switching among matching circuits of the power amplifier for each of frequencies has been proposed, for example.
For example, an output matching circuit for use in a variable frequency amplifier (triple-band power amplifier) is disclosed by the following nonpatent reference 1. This variable frequency amplifier switches among configurations of the output matching circuit by turning on and off two MEMS switches according to a frequency, thereby making it possible to establish matching at any of three frequencies.